Lift control device for stacks of sheets



Feb 28, 1967 A. SCHWEBEL 3,239,607

LIFT CONTROL DEVICE FOR STACKS OF SHEETS Filed July 16, 1964 l N VENTOR. A004 F S'C'fi/WEBEL BY Hm A T Ta avEYs 3,306,607 7 Patented Feb.28, 1967 3,306,607 LIFT CGNTRQL DEVICE FDR STACKS F SHEETS AdolfSchwebel, Offenbach am Main, Germany, assignor to Mabeg MaschinenbanG.m.b.H. Nachf., Hense & Pleines G.m.b.H. 2; (10., Offenbach am Main,Germany, a German company Filed July 16, 1964, Ser. No. 383,140 11Claims. (Cl. 271-31) The present invention relates to a control devicecontrolling motor-operated lifting means for lifting a stack or pile ofsheets which is gradually depleted by successive withdrawal of sheetsfor use in a sheet-using machine such as a printing press and, moreparticularly, to a control device of this kind in which a periodicallyup and down reciprocated foot presses against the top sheet of the stackin its lowermost position and controls the operation of the liftingmeans whereby the period of operation of the lifting means and with itthe extent of the lifting of the stack are preferably adjustable.

There are known control devices of the general kind above referred to inwhich the lifting of the stack is controlled by components of themachine such as the sheet pick-up means, the pressure foot, a stacklevel detector, etc., when and while successive sheets are withdrawnfrom the top of the stack. Such control devices include cams effectingactivation of the lifting means for a predetermined lifting of the stackin timed relationship with the level detecting means of the device. Anarrangement of this kind has the disadvantage that in high speedmachines the cams cause energization of the lifting means for a timewhich may be too short to effect the required lifting of the stack andin machines operating at low speeds for a time which is too long. As aresult the stack may not be lifted suificiently to be within theoperational reach of the sheet picl-up means, or it may be lifted sohigh that the pickup means are damaged.

Another known control device of the general kind above referred toattempts to eliminate the aforementioned disadvantage by meteringcurrent to the lifting means by means of the discharge of a capacitor.

In still another control device the power supply for the lifting meansis controlled by potentiometers. Such an arrangement requires asubstantially constant voltage supply which is not always available fromthe power means.

It is also known to provide a control device in which a periodicallyreciprocated slide supports suitable switching means controlling thestack lifting means in conjunction with a stack level detector. Such anarrangement requires a considerable number of heavy and thus ratherinert components and as a result the device is not suitable for the highspeed of modern machines in which the detector is only in very briefcontact with the top surface of the stac It is a broad object of thepresent invention to provide a novel and improved control device of thegeneral kind above referred to which is independent of the prevailingvoltage conditions and the specific material from which the sheets aremade and which is capable of operating either with high speed machinesor with low speed machines.

A more specific object is to provide a novel and improved control deviceof the general kind above referred to which assures that the stack as itis being depleted, is always lifted to a level which on One hand issufficient to bring the top level of the stack within the effectivereach of the sheet pick-up means and on the other hand does not causedamage to the sheet pick-up means.

Other objects, features and advantages of the invention will be pointedout hereinafter and set forth in the appended claims constituting partof the application.

Broadly, the invention resides in providing a pressure foot which alsofunctions as a stack-level detector and coacts, preferably by means of anose, with a movable intermediate control member in engagement with asec- 0nd displaceable control member whereby the position of the secondcontrol member is controlled by the position of the detector which inturn is controlled by the top level of the stack.

The second control member coacts at one end with a movable switchcontrol element which controls the switch controlling the power supplyfor the stack lifting means in accordance with the stack level. Said oneend of the second control element and the switch control element areseparated from each other by a preferably adjustable distance which iscontrolled by the top level of the stack so that the second controlmember will effect control of the power supply switch only when thestack is lifted through a distance corresponding to the aforementioneddistance between said one end of the second control element and theswitch control element.

In the single figure of the accompanying drawing a preferred embodimentof the control device according to the invention is shown by way ofillustration and not by way of limitation.

Referring now to the figure in detail, the figure shows a table 25supporting a stack or pile 2. The table is lifted by a power drive meanssuch as a motor 26, the operation of which is controlled by a switch 15.The table-lifting mechanism including the transmission means couplingtable 25 to motor 26 is conventional and does not constitute part of theinvention. Accordingly, it is not described or illustrated in detail.

Sheets are successively withdrawn from the top layer of stack 2thereby-gradually depleting the stack. The sheet pick-up means arediagrammatically indicated by a suction head 21 and also do notconstitute part of the invention.

Turning now to the control device according to the invention, the devicecomprises a foot 1 engageable with the top surface of stack 2. The foothas two purposes, one being to prevent an undesired transportation ordisplacement of the sheet or sheets just below the top sheet lifted bysuction cup 21 and the other being a detecting function to detectcontinuously the level of the stack and to control the level so that itis continually at the proper distance from the pick-up device 21.

To this end, foot 1 is moved periodically into and out of engagementwith stack 2 by means of bell crank lever 27 pivotal about a stationarypivot pin 28. Lever 27 has an arm 3 linked at 29 to foot 1 and mountinga nose 6 coacting with a first control member 7 and, more specifically,with a movable arm 8 thereof pivotal about a pivot pin 8a on the mainbody of control member 7. The second arm 4 of lever 27 mounts a roller4a constituting a cam follower coacting with a rotary camming surface 5.Foot 1 is at its upper end linked to an arm 30 which, in turn, ispivotal about a stationarily mounted pivot 31. As it is evident from theprevious description, rotation of camming surface 5 will impart to foot1 a combined lifting and swinging motion toward and away from stack 2.

Control member 7 is periodically reciprocated about a stationary pivot 9by means of a cam follower 11 coacting with a second rotary cammingsurface 10. Pivot 9 further supports a second control member 12 whichhas a nose portion 13 coacting with motor switch 15 controlling motor 26as previously stated. Control member 12 is coupled with control member 7by means of an adjustable set screw 14 which maintains members 7 and 12[ll]. a selected position in reference to each other.

A control pin 16 is slidable in control member 7. One end of pin 16abuts against pivotal arm 8. The other end of pin 16 is headed at 16a toretain pin 16 in member 7.

The angular position of arm 8 in reference to member 7 is controlled bya set screw 19. A loaded spring 20 maintains the hereinbefore describedsystem in equilibrium.

Pin head 16a coacts with a switch control element 17 disposed inalignment with pin 16 and lengthwise adjustable in reference thereto.Such control element constitutes an abutment element for the pin. Thedistance x between head 16a and the adjacent face of control element 17controls the distance through which stack 2 is lifted for eachoperational cycle of foot 1 and the components associated therewith.Suitable fastening means indicated as lengthwise grooves in controlelement 17 and a spring loaded ball 18 are provided to maintain controlelement 17 in any adjusted position, thereby preventing undesiredvariations of distance x and with it of the lift of stack 2 due toshocks and vibrations to which the control device may be exposed.

The energizing circuit for the motor may include a conventionalcapacitor-potentiometer assembly (not shown) to provide additional motorcontrol.

The operation of the control device as hereinbefore described, is asfollows:

In the position as shown it is assumed that switch 15 closes the motorcircuit so that stack 2 is being gradually lifted. As the lifting ofstack 2 continues, lever arm 3 through the agency of its nose 6 andpivot arm 8 will displace control pin 16 until pin head 16a reachescontrol element 17 in its adjusted position in control member 12.Continued lifting of stack 2 and with it continued lifting of controlpin 16 will cause tilting of control member 12 whereby switch 15 isopened thus stopping further lifting of stack 2 in the desired positionin reference to pick-up device 21.

Instead of continuous lifting of stack 2, the stack can also be liftedin small increments, namely by connecting and disconnecting the motorcircuit in accordance with the swinging movements of foot 1 correlatedwith the successive withdrawal of sheets. In this mode of operation thestepwise lifting of the stack will continue until the distance x isbridged by pin 16 and control member 12 is tripped as previouslydescribed.

The power to effect lifting of the stack may be supplied by anadequately dimensioned capacitor. The use of such a capacitor has theadvantage of protecting the entire installation against failures oraccidents as they may occur when the installation is operated, without astack on the table or without an appropriate table or prior to thesetting-up on the installation.

As it is apparent from the previous description, the control device ofthe invention is simple and inexpensive. It does not requirecomparatively slow and not very reliable relays. No specific electric orelectronic components are necessary, but merely simple mechanicalcomponents. Furthermore, the desired lifting distance as represented bythe distance x can be adjusted at any time, even when the machine isoperating by simply adjusting set screw 17.

While the invention has been described in detail with respect to acertain now preferred example and embodiment of the invention, it willbe understood by those skilled int he art, after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it is intendedtherefore to cover all such changes and modifications in the appendedclaims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A control device for controlling lifting means for lifting a stack ofsheets from which sheets are successively withdrawn by sheet pick-upmeans acting upon the top of the stack, said control device comprising aswitch means for controlling a power supply for said lifting means, amovable detector sensing the top level of the stack and engageabletherewith in pressure engagement, a first movable control memberengageable with said detector for positioning said control member by theposition of said detector, and a second movable control memberengageable with said switch means to actuate the same for disconnectingsaid power supply, said first control member including a support memberand a control pin slideable in said support member and engageable withsaid second control member, the lengthwise position of said pin beingcontrolled by said detector and controlling the position of said secondcontrol member in reference to the switch means, movement of thedetector into a position corresponding to a predetermined top level ofthe stack moving said pin into a position in which the second controlmember is positioned to engage the switch means for the purposeaforesaid.

2.. A control device according to claim 1 and comprising first mountingmeans pivotally supporting said support member, second mounting meanssupporting said detector displaceable up and down in reference to thetop level of said stack and swingable into and out of engagementtherewith, first rotary cam means coacting with said first mountingmeans to reciprocate the latter about its pivot axis and second rotarycam means coacting with the second mounting means to impart to saiddetector reciprocatory up and down movements and swinging movements intoand out of engagement with the top level of the stack.

3. A control device according to claim 1 wherein said second controlmember comprise a pivotally mounted support member and a control elementadjustable in reference thereto, the position of said control elementcontrolling the distance through which the first control member mustmove before engaging said second control member for controlling saidswitch means whereby the stack is lifted until the lifting meanstherefor are disconnected.

4. A control device according to claim 3 wherein said control elementcomprises a bolt gradually lengthwise displaceable in its support memberand thereby in reference to said first control member.

5. A control device according to claim 4 and comprising releasablelocking means for :locking said bolt in a selected lengthwise position.

6. A control device according to claim 5 wherein said locking meanscomprise lengthwise circumferentially spaced grooves in said bolt, and aspring-loaded ball engageable with any of said grooves.

7. A control device according to claim 1 wherein said movable detectorcomprises a foot movable into and out of pressure engagement with thetop layer of said stack and a nose moving in unison with said foot, andwherein said first control member includes a movable control elementeng-ageable with said nose and said pin, the position of said controlelement being controlled by said nose and controlling the lengthwiseposition of said pin, and wherein spring means bias said first controlelement into engagement with said nose.

8. A control device according to claim 7 comprising a support membersupporting said second control element lengthwise slidable in referencethereto, and limit means limiting the slid-able movement of said secondcontrol element toward said first control element.

9. A control device for controlling lifting means for lifting a stack ofsheets from which sheets are successively withdrawn by sheet pick-upmeans acting upon the top of the stack, said control device comprising aswitch means for controlling an electric power supply for said liftingmeans, a movable detector, means coacting with said detector forintermittently moving the same into a position of engagement with thetop of the stack for detecting the level thereof and into a positionlifted above the top of the stack, a lengthwise displaceable controlpin, a movable sensing member coacting with said detector forpositioning by the same and engaged with one end of said control pin fordisplacing the pin in accordance with the position of the detector, anda switch control member movable between a rest position disengaged fromsaid switch means and an operating position engaging said switch meansto operate the same for disconnecting said power supply, said switchcontrol member being engaged with the other end of said displaceablecontrol pin for movement of the switch control member into its operatingposition in response to a displacement of the pin by said sensingmember.

10. A :control device according to claim 9, wherein an abutment elementis movably supported on said switch control member, said abutmentelement being engageable with said other end of the control pin, andwherein adjustment means are provided on the switch control member foradjusting the position of said abutment element on the switch controlmember, thereby correspondingly varying the distance of displacement ofthe control pin before the same is engaged with the abutment element.

11. A control device according to. claim 10, wherein said adjustmentmeans are means for gradually varying the position of the abutmentelement in reference to the switch control member, and locking means forlocking the abutment element in a selected position on the switchcontrol member.

References Cited by the Examiner M. HENSON WOOD, JR., Primary Examiner.ROBERT B. REEVES, Examiner.

R. A. SCHACHER, Assistant Examiner.

1. A CONTROL DEVICE FOR CONTROLLING LIFTING MEANS FOR LIFTING A STACK OFSHEETS FROM WHICH SHEETS ARE SUCCESSIVELY WITHDRAWN BY SHEET PICK-UPMEANS ACTING UPON THE TOP OF THE STACK, SAID CONTROL DEVICE COMPRISING ASWITCH MEANS FOR CONTROLLING A POWER SUPPLY FOR SAID LIFTING MEANS, AMOVABLE DETECTOR SENSING THE TOP LEVEL OF THE STACK AND ENGAGEABLETHEREWITH IN PRESSURE ENGAGEMENT, FIRST MOVABLE CONTROL MEMBERENGAGEABLE WITH SAID DETECTOR FOR POSITIONING SAID CONTROL MEMBER BY THEPOSITION OF SAID DETECTOR, AND A SECOND MOVABLE CONTROL MEMBERENGAGEABLE WITH SAID SWITCH MEANS TO ACTUATE THE SAME FOR DISCONNECTINGSAID POWER SUPPLY, SAID FIRST CONTROL MEMBER INCLUDING A SUPPORT MEMBERAND A CONTROL PIN SLIDEABLE IN SAID SUPPORT MEMBER AND ENGAGEABLE WITHSAID SECOND CONTROL MEMBER, THE LENGTHWISE POSITION OF SAID PIN BEINGCONTROLLED BY SAID DETECTOR AND CONTROLLING THE POSITION OF SAID SECONDCONTROL MEMBER IN REFERENCE TO THE SWITCH MEANS, MOVEMENT OF THEDETECTOR INTO A POSITION CORRESPONDING TO A PREDETERMINED TOP LEVEL OFTHE STACK MOVING SAID PIN INTO A POSITION IN WHICH THE SECOND CONTROLMEMBER IS POSITIONED TO ENGAGE THE SWITCH MEANS FOR THE PURPOSEAFORESAID.